Public Land Mobile Networks (PLMNs) represent one example of the types of communication networks that can and do play a valuable role in public safety and information dissemination. For example, Release 8 of the Third Generation Partnership Project (3GPP) specifications provides for wireless system parts and associated system protocols referred to as the “Earthquake and Tsunami Warning System” or ETWS. The ETWS addresses a number of disaster situations and operates with the goal of collecting seismic sensor or other threat information and relaying to emergency points or other alert system nodes, for distribution to wireless devices. Release 9 included provisions for a Commercial Mobile Alert System (CMAS), which is designed to distribute alert signals to cellular users operating within the coverage area(s) of a cellular system. Further, the reader may refer to the 3GPP document “Technical Specification TS 22.268,” for details regarding the current state of the art for the 3GPP Public Warning System.
However, in a disaster or other type of national security or public safety (NSPS) situation, all or part of the cellular and local wireless network infrastructure may be impaired, e.g., may become damaged or otherwise become dysfunctional. Such infrastructure impairment degrades or eliminates communication services, at least within the affected areas. Further, the impairment of network infrastructure can result in unreliable and/or imprecise operation of the cellular location services (LCS) broadly relied upon for determining the geographic position of wireless devices operating within the network. The degradation or outright loss of reliable, accurate device positioning in NSPS situations has serious, potentially lethal consequences.
An example of such a situation is when a user equipment or “UE” loses cellular and wireless local network coverage and it does not have its own mechanism for determining its location, or is operating in an enclosed space or other environment where its onboard positioning system operates poorly or not at all. Device-based location mechanisms include Global Navigation Satellite System (GNSS) circuits, such as a Global Positioning System (GPS) circuitry, Galileo-based circuitry, etc. Such systems may use network assistance, e.g., Assisted GNSS (A-GNSS) and thus are vulnerable to a loss of assistance data arising from impairment of the network infrastructure, or arising from movement of the device into a location that prevents the reliable reception of the assistance data.
The impairment of network-provided and/or network-assisted positioning, broadly referred to as “infrastructure based positioning” to denote the reliance on the network for device positioning, at best leaves the device owner or operator with an unreliable estimate of the device's position. At worst, the device owner or operator is left without any positioning information. Here, the phrase “device owner or operator” denotes any person, machine or system that uses or includes a wireless communication device for communication network services, including LCS. Non-limiting examples of such devices include feature phones, smartphones, machine type communication devices or machine-to-machine (M2M) communication devices, target devices, embedded or integrated devices, USB-dongles, network modems or other wireless adaptors, in-vehicle communication modules, etc.
Further, there are many types and/or variations of “infrastructure based positioning.” One example is the aforementioned A-GNSS approach. Other examples include Observed Time Difference of Arrival (OTDOA) positioning methods, Uplink Time Difference of Arrival (UTDOA) positioning methods, enhanced Cell ID (E-CID) based positioning methods, and various hybrid methods, such as a combination of A-GNSS and OTDOA-based measurements. These techniques implicate any number of network infrastructure entities beyond the base stations and their backhaul and side-haul links, such as Location Measurement Units (LMUs) serving as measurement nodes for uplink signals from wireless devices operating within the network, or, in the case of Long Term Evolution (LTE) networks, one or more Enhanced Serving Mobile Location Centers (E-SMLCs).
Against this backdrop, the 3GPP SA1 working group is studying the feasibility of Proximity Services (ProSe) for national security and public safety use cases. Refer, for example, to the technical report, 3GPP TR 22.803 “Proximity Services (ProSe)”. Such proximity services can be provided by direct device-to-device (D2D) communications, in which two or more devices communicate via a direct communication link, rather than communicating through a cellular base station (BS) or a wireless local area network (WLAN) access point (AP) or a relay. In the LTE context, this type of communication is referred to as “LTE Direct.”
Because D2D communications utilizing LTE Direct or some other ad hoc networking technology, such as Bluetooth or WiFi Direct, can take place even with limited or no infrastructure support, it is identified as an important technology enabler for ProSe in a catastrophe or other emergency situations.
However, peer-to-peer cooperative positioning methods, in which peer wireless devices exchange positioning information to determine and/or refine their respective positioning determinations, generally still rely on the availability of cellular or WLAN access points with respect to at least some of the peer devices involved in cooperative positioning. For example, wireless devices operating in a GNSS-hostile environment (e.g., indoors) or devices without GNSS capability receive peer positioning information from one or more other wireless devices that know their absolute positions as a consequence of network-assisted or network-performed positioning. LTE Direct or other D2D communication within the cellular network radio spectrum may be used for D2D communications, for peer-based device positioning, communication with proximate first responders, etc.
Known approaches to implementing D2D communications consider radio resource availability, network load, radio propagation conditions, and other physical and lower-layer parameters. In general, the current algorithms used for activating D2D communications tend to select devices for D2D communications based on minimizing the interference caused by such devices, which results in the selection of devices that are more distant from the cellular base stations and/or other wireless access points. However, it is recognized herein that such approaches do not consider the various degradations in infrastructure positioning accuracy and reliability that may occur with even a partial impairment of network infrastructure.